.k-header{
    display: flex;
    position: fixed;
    box-sizing: border-box;
    width: 100%;
    max-width: 640px;
    height: 2.3rem;
    line-height: 2.3rem;
    text-align: center;
    top: 0;
    z-index: 200;
    border-bottom: 1px solid #ddd;
    background: #f8f8f8;
}
.k-header > .left{
    flex-basis: 3rem;
    text-align: center;
    flex-shrink: 0;
}
.k-header > .middle{
    flex-grow: 1;
    overflow: hidden;
    white-space: nowrap;
    text-overflow: ellipsis;
}
.k-header > .right{
    flex-basis: 3rem;
    text-align: center;
    flex-shrink: 0;
}